全文获取类型
收费全文 | 424775篇 |
免费 | 47823篇 |
国内免费 | 162篇 |
出版年
2018年 | 3902篇 |
2016年 | 5280篇 |
2015年 | 6896篇 |
2014年 | 8145篇 |
2013年 | 11232篇 |
2012年 | 12782篇 |
2011年 | 13232篇 |
2010年 | 9075篇 |
2009年 | 8429篇 |
2008年 | 12110篇 |
2007年 | 12608篇 |
2006年 | 11828篇 |
2005年 | 11302篇 |
2004年 | 11345篇 |
2003年 | 10628篇 |
2002年 | 10451篇 |
2001年 | 17417篇 |
2000年 | 17433篇 |
1999年 | 13911篇 |
1998年 | 5019篇 |
1997年 | 5270篇 |
1996年 | 4911篇 |
1995年 | 4616篇 |
1994年 | 4486篇 |
1993年 | 4536篇 |
1992年 | 11611篇 |
1991年 | 11537篇 |
1990年 | 11296篇 |
1989年 | 10907篇 |
1988年 | 10488篇 |
1987年 | 10076篇 |
1986年 | 9362篇 |
1985年 | 9231篇 |
1984年 | 7748篇 |
1983年 | 6703篇 |
1982年 | 5161篇 |
1981年 | 4617篇 |
1980年 | 4463篇 |
1979年 | 7422篇 |
1978年 | 5864篇 |
1977年 | 5396篇 |
1976年 | 5201篇 |
1975年 | 5594篇 |
1974年 | 6300篇 |
1973年 | 6166篇 |
1972年 | 5764篇 |
1971年 | 5226篇 |
1970年 | 4633篇 |
1969年 | 4574篇 |
1968年 | 4421篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
172.
173.
174.
E. Molina Grima J. A. Sánchez Pérez F. García Camacho F. G. Acién Fernández J. M. Fernández Sevilla F. Valdés Sanz 《Biotechnology letters》1994,16(10):1035-1040
Summary Eicosapentaenoic acid (EPA) volumetric productivity from an outdoor chemostat culture ofPhaeodactylum tricornutum UTEX 640 in a 50-l tubular photobioreactor varies with dilution rate, reaching a maximum of 47.8 mg l–1 d–1 at D=0.36 d–1. Continuous culture at high dilution rates' is proposed as the most adequate operating mode to maximize polyunsaturated fatty acid production. 相似文献
175.
Human placental tissue stimulates bovine capillary endothelial cell growth,migration and protease production 总被引:2,自引:0,他引:2
A crude extract of human placenta has been demonstrated to stimulate growth, motility and the production of the proteases plasminogen activator and collagenase in cultured bovine capillary endothelial cells. These data are in keeping with the presence of an angiogenic factor(s) in human placenta. 相似文献
176.
G A Vilkov E M Stepanenko T A Khoruzhaia 《Biulleten' eksperimental'no? biologii i meditsiny》1985,99(1):48-50
The authors studies the effects of blood serum and IgG fraction from dogs immunized with brain and blood sera from patients with multiple sclerosis and schizophrenia on lipid peroxidation in rat brain homogenates. Measured the content of diene conjugates (DC) and malonic dialdehyde (MDA) in the rat brain after administering the IgG fraction. It was established that antioxidant activity of blood sera and IgG fraction from control animals and donors was significantly higher as compared to experimental. Administration of the IgG fraction brought about an increase in the content of DC and MDA in the brain of experimental animals. It is concluded that complement-dependent brain antibodies present in the blood serum of patients with schizophrenia and multiple sclerosis potentiate lipid peroxidation in the cerebral tissue and that the unsophisticated and informative method for antibody determination may be used in clinical practice. 相似文献
177.
178.
179.
180.
In C4 plants phosphoenolpyruvate (PEP) of the C4 cycle may betransported on a chloroplast transporter which also transports3-phosphoglycerate (3-PGA) and triosephosphates. In C3 plantsPEP is not considered to be effectively transported on the chloroplastphosphate translocator. The influences of certain organic phosphates,having a similar structure to either PEP or triose-phosphates,on 3-PGA dependent O2 evolution by C4 (Digitaria sanquinalisL. Scop.) and C3 (Hordeum vulgare L.) mesophyll chloroplastswere investigated. In the C4 mesophyll chloroplasts phosphoglycolatewas a competitive inhibitor (Ki = 2.1 mM) of 3-PGA dependentO2 evolution, and was as effective as previously reported forPEP. 2-Phosphoglycerate was also a competitive inhibitor (Kt= 8.6 mM) of O2 evolution in the C4 mesophyll chloroplasts with3-PGA as substrate, while phospholactate was a weak inhibitorand glyphosate had no effect. Neither PEP, phosphoglycolatenor 2-phosphoglycerate were effective inhibitors of 3- PGA dependentO2 evolution in the C3 chloroplasts. Phosphohydroxypyruvatewas a competitive inhibitor of 3-PGA dependent O22 evolutionin both chloroplast types. The selectivity in inhibition ofO2 evolution with 3-PGA as substrate suggests that the C4 mesophyllchloroplasts can recognize certain organic phosphates with thephosphate in the C-2 or C-3 position but that the C4 mesophyllchloroplasts can only effectively recognize certain organicphosphates with the phosphate in the C-3 position. The resultsalso support the view that 3-PGA and PEP are transported onthe same phosphate translocator in C4 mesophyll chloroplasts.
1 Current address: Department of Horticulture, 2001 Fyffe Court,The Ohio State University, Columbus, Ohio 43210-1096. (Received March 24, 1987; Accepted April 16, 1987) 相似文献